1. Field
The present invention relates generally to wireless telecommunication devices, and in particular to wireless telephones.
2. Background
Background noise is an inherent problem in wireless telephone communication. Conventional wireless telephones include a single microphone that receives a near-end user's voice and outputs a corresponding audio signal for subsequent encoding and transmission to the telephone of a far-end user. However, the audio signal output by this microphone typically includes both a voice component and a background noise component. As a result, the far-end user often has difficulty deciphering the desired voice component against the din of the embedded background noise component.
Conventional wireless telephones often include a noise suppressor to reduce the detrimental effects of background noise. A noise suppressor attempts to reduce the level of the background noise by processing the audio signal output by the microphone through various algorithms. These algorithms attempt to differentiate between a voice component of the audio signal and a background noise component of the audio signal, and then attenuate the level of the background noise component.
Conventional wireless telephones often also include a voice activity detector (VAD) that attempts to identify and transmit only those portions of the audio signal that include a voice component. One benefit of VAD is that bandwidth is conserved on the telecommunication network because only selected portions of the audio signal are transmitted.
In order to operate effectively, both the noise suppressor and the VAD must be able to differentiate between the voice component and the background noise component of the input audio signal. However, in practice, differentiating the voice component from the background noise component is difficult.
In addition to background noise, transmission channel impairments can degrade the quality of an audio signal. For example, the audio signal encoded and transmitted by the near-end user's wireless telephone may be corrupted by transmission channel impairments, and this may cause quality degradation of the audio signal received and decoded by the far-end user's wireless telephone. In this example, the near-end user's wireless telephone cannot, by itself, remedy all the adverse effects of transmission channel impairments.
What is needed then, is a wireless telephone that better mitigates the effect of background noise present in an input audio signal as compared to conventional wireless telephones, and a transmission system that provides redundancy to combat transmission channel impairments.